Quantification of Methyl Transferase and Ethylene Production in Berry Skins

MT was extracted and determined according to the methods of Xu et al^{5 (link)}. The primary extraction procedures included preliminary extraction via an ultrasonic bath in methanol, evaporation of the extraction solution to dryness, and purification of the extract using a C₁₈ solid-phase extraction cartridge (ProElut^TM; Dikma, China). MT was determined using an UHPLC-MS system in conjunction with an ACQUITY UHPLC system and a QTOF micro–mass spectrometer (Waters, Milford, MA, USA). The parameters were as follows: mobile phase, 0.05% (v/v) acetic acid and methanol at 0.3 ml min⁻¹; column temperature, 25 °C; capillary temperature, 300 °C; spray voltage, 3000 V; auxiliary pressure, 15 V; and sheath pressure, 35 V.
Five grams of berry skin was enclosed in a 100-mL jar and incubated for 3 h at 25 °C. Five milliliters of the headspace gas was then withdrawn from each jar using an air-tight syringe for ethylene determination. The ethylene concentration was determined using a GC-9A gas chromatograph (Shimadzu, Kyoto, Japan). The ethylene production rate was calculated on the basis of the ethylene concentration, incubation time, and skin weight^{5 (link)}.